Since I just started to add support for "old" FrSky XSRF3O flight controller to INAV (expect this in a release after 1.8) it might be a good idea to share few words about it.

FrSky XSRF3O flight controller in a box

First of all, it comes in a box. Why am I mentioning this? Because none of my flight controllers, and I own at least more than a dozen, came in box. C'mon, this is huge! I'm not joking, this is really a nice touch.

FrSky XSRF3O flight controller in electrostatic bag

Inside a box, a bag and a label. With almost all technical details. Not worth writing more about it.

FrSky XSRF3O flight controller full view

Inside a bag, flight controller itself. Oh, did I mentioned it has a build in FrSky receiver? No? Well, it has XSR receiver (XSRF3O, get it? XSR). Internally it is connected via S.Bus to UART2 (RX pin) and via SmartPort to UART3 (TX pin). And that leaves only UART1 available for a user. Should be enough, since there is a possibility to use SoftwareSerial on PWM5-8 outputs.

FrSky XSRF3O flight controller bottom

What else? OSD, of course. And SD Card slot. But slot is positioned in a stupid place: above CPU, in a middle of a board. Just try to take this card out to download the logs in a tight build. Or stacked below RunCam Split. Good luck...

FrSky XSRF3O flight controller top

Oh, another great feature: PCB is conformally coated. Kudos for FrSky for that! Do you want to know another bad feature? Lack of I2C. Board is designed for racers, but I2C would be a nice touch...

Bottom line? Although it has few drawbacks, it might be a really nice flight controller and I already have an idea where I will put it...